Optical signal loss may occur in a long length of an optical fiber or at an interface between two optical devices, such as at a connection between an optical fiber and another optical device. The condition of the optical signal communicated by the optical fiber to an optical device is important to the proper operation of the optical device. For example, if the optical signal is absent, attenuated, or otherwise degraded, the optical device may malfunction. Several techniques attempt to detect these conditions and provide protection switching to maintain communication.
One approach described in BellCore Technical Reference No. TR-NWT-001073 resolves this problem by splitting the optical signal into a primary component and a secondary component, and sampling the secondary component of the optical signal to determine the condition of the optical signal prior to communicating the optical signal to the optical device. This approach attenuates the optical signal by at least the amount of the secondary component and may create additional insertion losses in the optical signal.